Compactor

ABSTRACT

There is disclosed a domestic refuse compactor having an improved mechanism for compressing refuse in an open top container. The mechanism comprises a pressure plate for contacting the refuse, a screw member in driving engagement with the pressure plate, means for reciprocating the screw and a linkage mechanism independent of the screw for maintaining the pressure plate generally horizontal.

United States Patent 1191 1111 3,921,515

Eckerle et al. Nov. 25, 1975 [54] COMPACTOR 1,738,326 12/1929 31111111.... 100/229 R x 3,603,247 9/1971 Price et al 100/295 x [75] lnvemors- 3,654,855 4 1972 Longo 100/229 A Hardy, both of Loulsvllle, 3,714,890 2/1973 Moon 100/229 A 3,727,546 4/1973 McKinney 100/229 A [73] Asslgnee' t'gz j f z Company 3,741,108 6/1973 Stratman et a1. 100/229 A 3,756,150 9/1973 Bourgeois 100/229 A [22] Filed: Apr. 26, 1974 21 APPL 4 4 507 Primary Examiner-Billy J. Wilhite [52] US. Cl 100/229 A; 100/289; 100/295 ABSTRACT [51] 1111.01. B3013 1/18 There is disclosed a domestic refuse Compactor having an improved mechanism for compressing refuse in an open top container. The mechanism comprises a pressure plate for contacting the refuse, a screw member [58] Field of Search 254/98, 126; 100/258, 289, 100/229 R, 229 A, 290, 295; 53/124 B; 141/73 [56] References C'ted in driving engagement with the pressure plate, means UNITED STATES PATENTS for reciprocating the screw and a linkage mechanism 38,333 4/1863 Ray 100/289 X independent of the screw for maintaining the pressure 279,854 6/1883 Belt 100/229 A plate generally horizontal. 1,312,313 8/1919 Dovi 100/289 X 1,675,669 7/1928 Snyder 100/229 A 7 Claims, 6 Drawing Figures US. Patent Nov. 25, 1975 Sheet 2 of5 3,921,515

/ i MW. Al in N US. Patent Nov. 25, 1975 Sl leet4of5 3,921,515

U.S. Patent Nov. 25, 1975 Sheet50f5 3,921,515

COMPACTOR Domestic refuse compactors are, of course, commercially available appliances. Compactors of this type normally include a cabinet having a front opening, a door for closing the opening, an open top container movable into and out of the cabinet, and a press or compacting mechanism mounted in the cabinet for downward movement into the open top container for compressing refuse therein. Many of the compactors presently on the market incorporate a screw driven linkage arrangement for applying force to the pressure plate. Devices of this type have an inherent disadvantage since the mechanical advantage or disadvantage of linkage arrangement varies as a function of the position of the pressure plate.

The maximum force requirement of a domestic compactor generally occurs during crushing of a bottle. Since a bottle may encounter the pressure plate at any position during the travel thereof, it is desirable that the compacting mechanism generate forces which are generally constant and independent of the vertical position of the pressure plate. This feature appears to be either intentionally or inherently provided by the prior art compactors so long as these compactors do not encounter an eccentric load. In the prior art mechanism for horizontally stabilizing the pressure plate incorporates the screw threads of the driving mechanism. Thus the encounter of an eccentric high load item tends to bind the screw and causing an increase in frictional loads thereby decreasing the useful output of the compacting mechanism at a time when the maximum force is required. It will be apparent that eccentric high loads are probably more common than concentric high loads since there are more eccentric locations on the pressure plate than concentric locations. Thus, these prior art devices must be overdesigned in order to achieve a maximum useful force sufficient to crush an eccentric high load item.

Domestic refuse compactors presently on the market may be classified into two general size categories. A full size compactor produces a compacted refuse mass in the range of 1.1-1.4 cubic feet and is of substantially countertop height, i.e. 33-36 inches high. There are also available smaller compactors which produce a compacted refuse mass on the order of about 0.5 cubic feet and are sufficiently short to fit underneath a sink. These smaller compactors are basically miniatures of the full size compactors. An important feature of this invention is that this compactor produces compacted refuse mass in the size range of a full sized compactor and yet is short enough to fit beneath a conventional sink.

It is an object of this invention to provide a compactor having an improved screw driven press mechanism incorporating an arrangement independent of the screw for maintaining the pressure plate in a predetermined position during compacting.

Another object of the invention is to provide a full sized domestic refuse compactor having an improved press mechanism enabling the compactor to fit beneath a conventional sink. I

In summary, one aspect of this invention comprises a compactor including a frame providing a compacting chamber having an access opening thereinto, a door mounted for movement between positions opening and closing the access opening, an open top container in the chamber, a pressure plate for movement into and out of the container for compressing refuse therein, and means for vertically reciprocating the plate including a screw, means mounting the plate on the screw, and means for driving the screw, and means bearing between the plate and the frame independently of the screw for maintaining the plate generally horizontal during downward movement toward the container.

In summary, another aspect of the invention comprises a compactor for use beneath a kitchen counter having therein a sink providing a bottom at a predetermined elevation above a floor and a drain including a section extending downwardly from the sink at a location away from the sink front and a section extending generally horizontally for connection to a plumbing line, the drain wholly residing; above a second predetermined elevation above the floor and below the first elevation from a predetermined distance away from the sink front, the compactor comprising a cabinet having a compacting chamber therein opening through the cabinet front, a door closing the opening and a rear section terminating below the second elevation for positioning below the drain; an open top container in the chamber; and a pressure plate and means including a vertically movable element forwardly of the rear cabinet section for moving the pressure plate downwardly into the open top container for compressing refuse therein and for moving the plate upwardly out of the container in response to upward movement of the element, the element being at least partially between the first and second elevations when the pressure plate is out of the container.

In the drawings:

FIG. 1 is a side view, partly in section, illustrating the compactor of this invention, the compacting mechanism being in its uppermost position;

FIG. 2 is a front view, partly in section, of the compactor of FIG. 1 illustrating the compacting mechanism in its lowermost position;

FIG. 3 is a vertical cross sectional view of the compacting mechanism of FIGS. 1 and 2 taken substantially along line 33 of FIG. 2;

FIG. 4 is a horizontal cross sectional view of the compacting mechanism of FIG. 2 taken substantially along line 44 thereof;

FIG. 5 is a horizontal cross sectional view of the compactor of FIG. 1 taken substantially along line 55 thereof; and

FIG. 6 is an isometric view of one part of a scissors link arrangement utilized in the compactor of FIGS. 1-5.

Referring to FIGS. 1 and 2, there is illustrated a compactor 10 positioned beneath a sink 12 and comprising as major components a cabinet or frame 14, a door 16, a refuse container 18, and means 20 for compacting or compressing refuse in the container 18 in response to signals from suitable controls (not shown).

The sink 12 has a front wall (not shown) and a bottom wall 24 opening into a drain line 26 rearwardly from the front wall. As is conventional, the drain line 26 extends downwardly from the sink bottom 24 a short distance and then extends generally horizontally for connection to a plumbing line. conventionally, the sink bottom 24 is a predetermined distance from the kitchen floor 28 while the bottom of the drain line 26 is a second lesser predetermined distance from the floor 28.

The cabinet or frame 14 may be of any suitable design and is illustrated as being of rectilinear configuration having a top wall 30, side walls 32, 34, a back wall 36 and a bottom wall or floor 38. The frame 14 is supported from the floor 28 by suitable adjustable feet 40. It will accordingly be seen that the cabinet 14 provides a compacting chamber 42 having a front access opening 44 thereinto.

The door 16 may be mounted in any suitable fashion for movement between open and closed positions in order to provide access to the compacting chamber 42. The door 16 may be pivotally mounted by upper and lower pins 46 which extend through upper and lower brackets 48.

The container 18 is preferably a one-piece plastic molding substantially cylindrical in shape although it may be tapered slightly in order to be removed from its mold. A bracket 50 extends circumferentially about the container 18 providing a groove for receiving a support carried by the door 16. At the upper end of the container 18, there is provided a clamp 52 which likewise may provide means for attachment to the door 16. The container 18 is preferably carried by the door 16 during opening and closing movement thereof in order to move the container out of and into the compacting chamber 42. Accordingly, the mounting mechanism for the container 18 is preferably as disclosed in US. application Ser. No. 476,528. Such an arrangement facilitates manipulation of the cylindrical container 18 through the access opening 44 and allows the container to move downwardly to besupported by base 38 during the compacting operation. In the alternative, the container 18 may be mounted on the door 16' for simple pivotal movement therewith if the side walls 32, 34 are spaced apart sufficiently or the door 16 may by slidably mounted on the cabinet 14.

The compacting mechanism 20 includes as major components a pressure plate 54, means 56 for vertically reciprocating the plate 54 and means 58 bearing between the plate 54 and the frame 14 for maintaining the plate 54 generally horizontal during downward movement toward and into the container 18.

The pressure plate 54 may be of any suitable design and conveniently includes a generally circular plate 60 sized to be received in the container 18. The plate 60 provides a pair of ribs 62 on the underside thereof to provide increased rigidity and to act as bottle breakers.

As shown in FIG. 3 the reciprocating means 56 includes a screw 64 having the lower end thereof secured in a ball type bearing element 66 in any suitable fashion, as by a pin 68. The ball bearing element 66 is captivated to the plate 60 by a substantially hemispherical cup 70 having an opening 72 therein receiving the screw end. The cup 70 is attached to the pressure plate 54 in any suitable fashion, as by conventional threaded fasteners 74. It will accordingly be seen that the pressure plate 54 is mounted for tilting movement relative to the screw 64 about a plurality of horizontal axes.

The upper end of the screw 64 is received in an internally threaded sleeve 76 which is secured to a substantially spherical bearing element 78. A plurality of drive pins 80 project radially from the bearing element 78 into a like plurality of drive slots 82 provided by a collar 84. The collar 84 provides an internal seat 86 mating with the exterior of the bearing element 78. A retainer 88 is releasably secured to the open bottom end of the collar 84 in any suitable manner, as by a screw connection (not shown) in order to captivate the bearing element 78. It will accordingly be seen that rotation of the collar 84 causes rotation of the sleeve 76 through the drive connection afforded by the pins and the slots 82 to thereby reciprocate the screw 64. It will also be seen that the screw 64 is capable of limited tilting movement relative to the collar 84 because of the bearing 78, 86 and the vertical extent of the slots 82.

The collar 84 provides an external upwardly facing shoulder 90 captivating a needle or roller bearing 92 against a generally horizontal flange 94 abutting against a plate 96. As will be more fully pointed out hereinafter, the plate 96 acts to transmit forces generated during compacting t0 the frame 14. The flange 94 carries a tubular bearing section 98 extending through the plate 96.

Positioned above the top wall 30 is a bearing plate 100 and rotating collar 102. The collar 102 is interiorally splined to provide a driving connection between the collars 102, 84. The collar 102 is also externally splined to provide driving connection to a large toothed wheel 104 illustrated in FIG. 1. The collar 102 is captivated to the collar 84 by a suitable retainer 106. It will be seen that the collar 102 and toothed wheel 104 are mounted for rotation about an axis 108 defined by the tubular bearing section 98.

A cog belt 110 drivably connects the toothed wheel 104 to a similar gear wheel 112 carried on an output shaft 114 of a motor 116 suspended from the top wall 30 of the frame 14 by suitable releasable fasteners 118. As shown best in FIG. 1, it will be apparent that the dimensions of the horizontal maintaining means 58 are such that the motor 116 may neatly be placed in the compacting chamber 42.

Driving the motor 116 causes driving movement of the belt 110 which rotates the collar 84 about its axis 108. Because of the drive connection between the pins 80 and slots 82, the internally threaded sleeve 7 rotates and moves the screw 64 either up or down depending on the direction of rotation of the sleeve 76.

It should be noted that the externally threaded screw 64 reciprocates while the internally threaded sleeve 76 rotates but does not reciprocate. As illustrated best in FIGS. 1 and 3, the bottom of the sleeve 76 is disposed well within the compactor 10 at a location where the pressure plate 54 clears the container 18 upon the termination of upward movement of the screw 64. Thus the length of the stroke of the screw 64 is measured from adjacent the bottom of the sleeve 76 rather than from the plane of the toothed wheel 104. As shown best in FIG. 1, the datum 124 represents the lowermost point of travel of the ribs 62. Accordingly, the stroke of the screw 64 is substantially equal to the distance between the datum 124 and the ribs 62 in the uppermost position of the pressure plate 54. Since about half of the screw 64 is below the top of the compactor 10 in the uppermost position of the screw 64, it will be apparent that the overall height of the compactor 10 has been substantially reduced. Accordingly, the screw 64 is positioned beneath the sink 24 above the bottom of the drain 26 in the uppermost screw position. It will accordingly be apparent that the compactor 10 may be placed underneath a conventional sink in large measure because the screw 64 reciprocates from a midposition substantially below the top of the compactor 10.

It is apparent from FIG. 1 that a rear section of the compactor 10 resides below the bottom of the drain 26 while the screw 64 at least partially resides in the space between the bottom of the drain 26 and the bottom 24 of the sink 12. A cover 126 may be secured to the frame 14 for enclosing the upper end of the screw 64.

It will be noted that the screw 64 is directly connected to the pressure plate 54 rather than being connected thereto through a linkage mechanism. Thus the resistance to movement sensed by the screw 64 is the resistance due to compacting refuse rather than a mechanical disadvantage appearing in a linkage arrangement. Accordingly, the full output of the motor 116, with the exception of any friction losses, is delivered to the pressure plate 54 at all vertical positions of the screw 64. Thus the compacting force delivered by the compacting means is relatively constant and inde pendent of the vertical position of the pressure plate 54.

The means 58 for maintaining the pressure plate 54 horizontal during downward movement thereof constitutes an important part of this invention. It is, of course, widely realized that the pressure plate 54 should retain a predetermined attitude during compressing movement into the container 18. Since the container 18 is desirably vertical, the pressure plate 54 should remain substantially horizontal although both could conceivably be tilted if desired. As will become more fully apparent hereinafter, the maintaining means 58 bears between the pressure plate 54 and the frame 14 independently of the screw 64 and sleeve 76.

The maintaining means 58 comprises first and second scissors links 128, 130 secured together by suitable fasteners 132, 134 which define an axis 136 of relative pivotal movement, a reaction structure 138 for transmitting forces from the pressure plate 54 to the links 128, 130 and a reaction structure 140 for transmitting forces from the links 128, 130 to the frame 14 of the compactor 10.

As shown best in FIGS. 2 and 3, the first scissors link 128 comprises a pair of parallel elongate plates 142, 144 which are rigidly interconnected by upper and lower cross members 146, 148. Each of the cross members 146, 148 carries a pair of journaled wheels 150, 152 respectively.

The second scissors link 130 comprises a pair of symmetrical members 154, 156 as may be seen by a comparison of FIGS. 3, 4 and 6. Each of the members 154, 156 comprises a flat plate 158, 160 providing an enlarged opening 162, 164 therethrough for passing the screw 64. Each of the members 154, 156 also comprises a flange 166, 168 adjacent the openings 162, 164

respectively and a flange 170, 172 extending the full length of the respective member 154, 156. The members 154, 156 are secured, as by welding or the like, to upper and lower cross members 174, 176 which carry respectively a pair of journaled wheels 178, 180. The members 154, 156 are preferably welded together along the junction of the flanges 166, 170; 168, 172 with the plate 158, 160 respectively. It will accordingly be seen that the scissors links 130 comprises a rectangular structure having substantial strength both in torsion and in compression.

The fasteners 132, 134 may be of any suitable type and are illustrated in FIGS. 3, 4 and 5 as comprising elongate pins having integral heads on one side thereof and a keeper 182, 184 on the inside of the link 130. Access to the keepers 182, 184 is provided by a suitable opening in the flanges 166, 168 as seen in FIGS. 5 and 6.

For purposes more fully explained hereinafter, the first scissors link 128 is pivotally connected adjacent the lower end thereof to the reaction structure 138 and is pivotally connected adjacent the upper end thereof to the reaction structure 140. Accordingly, there is provided a pair of lower links 186 secured at one end thereof to the plates 142, 144 by suitable fasteners 188. The links 186 provide an offset lower end having a pin 190 extending through a suitable opening in the reaction structure 138. There is also provided a pair of substantially identical but slightly longer upper links 192 having one end thereof secured to the plates 142, 144 by suitable fasteners 194 and having an offset upper end providing a pin 196 extending through a suitable opening in the reaction structure 140. As will be apparent hereinafter, the pins 190, 196 reside in horizontal planes defined by the path of movement of the wheels 152, 180; 150, 178 and define an axis intersecting th screw 64.

The lower reaction structure 138 comprises a generally C-shaped channel 198 having a web 200 captivated by the cup and fasteners 74 to the pressure plate 54, a pair of upstanding flanges 202 and a pair of relatively short horizontal flanges 204. Inside the C-channel 198 is a channel 206 having a web 208 providing an opening 210 of sufficient size to pass the screw 64 and provide access to the fasteners 74 as may be seen in FIGS. 3 and 4. The channel 206 also provides upstanding flanges 212 parallel to the flange 202. As shown best in FIG. 2, the outermost ends 214 of the web 208 are turned down to provide increased rigidity. The'channels 198, 206 are rigidly interconnected, as by welding or bolting. As shown best in FIG. 3, the flanges 202, 212 provide aligned apertures to receive the pins 190.

The reaction structure is conveniently of similar design to the structure 138. Accordingly, the reaction structure 140 comprises a generally C-shaped channel 216 having the plate 96 as the web thereof. The channel 216 also comprises a pair of downwardly facing flanges 218 and a pair of short generally horizontal flanges 220. Inside the channel 216 is another channel 222 having a web 224 providing a central opening 226 for passing the collar 84. Extending from the web 224 adjacent the opening 226 are a pair of flanges 228. The channel 222 also comprises a pair of downwardly extending flanges 230 parallel and closely adjacent to the flanges 218 of the C-channel 216. As shown best in FIG. 2, the outermost ends'232 of the web 224 are upturned to provide additional rigidity for the web 224. As shown best in FIG. 3, the flanges 218, 230 provide aligned apertures for receiving the pins 196 of the links 192. The channels 216, 222 are preferably rigidly interconnected, as by welding or bolting.

During operation when the pressure plate 54 does not eccentrically contact a high load item, eg a bottle, downward movement of the screw 64 causes the wheels 152, 150, 178 to bear substantially evenly against the respective webs or tracks 208, 222. Since the trackway defined by the flanges 220 and the web 222 is horizontal and fixed, the opposite ends of the scissors links 128, 130 remain horizontal regardless of the relative angular position therebetween. As the pressure plate 54 approaches its lower limit of movement, the cross members 146, 174 may engage the flange 228 thereby causing the motor 116 to stall out or a suitable control may be activated to de-energize the motor 116. During retraction of the pressure plate 54, the links 128, 130 pivot to become more nearly horizontal thereby opening the scissors. Without the links 186, 192, the wheels 152, 180 could conceivably escape from the trackway provided by the flanges 204 and the web 208. It will be evident, however, that the distance from the pin 190 to the fastener 188 plus the distance from the fastener 188 to the axis of the wheel 152 is less than the distance between the pin 190 and the end of the web 208. Thus, the links 186 tie the links 128, 130 to the reaction structure 138.

It will be noted that the fasteners 132, 134 are not centered along the links 128, 130. From FIG. 2, it will be apparent that the upper wheels 150, 178 have a longer track on which to run than do the lower wheels 152, 180. It is desirable that the channels 216, 222 run substantially the width of the cabinet 14 in order to efficiently transfer loads to the vertical members thereof. In order to accommodate the different travel of the upper and lower wheels, the pivot connections 132, 134 are disposed closer to the lower end of the scissors links 128, 130. It will also be noted that the link 192 is longer than the link 186 in order to accommodate the different length of travel of the upper and lower wheels.

An important feature of the maintaining means 58 is that the pressure plate 54 remains substantially horizontal even upon engaging a high eccentric load. For example, it may be assumed that the plate 54 contacts a high load item (e.g., a bottle) midway between the parallel planes defined by the respective edges of scissors links 128 and 130. Such a high load item is represented by the arrow 234 in FIG. 2. This load tends to pivot the pressure plate 54 and reaction structure 138 in a counterclockwise direction about a horizontal axis extending through the bearing element 66. The web or track 208 tends to move toward the wheels 152 and places an increased compression load on the portion of link 128 between its point of attachment to wheels 152 and fasteners 132, 134. correspondingly, the web or track 208 tends to move away from the wheels 180 and the flanges 204 tend to move toward the wheels 180 to place the link 130 in tension between its point of attachment to wheels 180 and fasteners 132, 134. Similarly, the wheels 174 come into bearing engagement with the flanges 226 of the reaction structure 140 and place link 130 in compression from the point of attachment of wheels 174 to fasteners 132, 134. Also, the wheels 150 bear against the web 220 of the reaction structure 140 and place link 128 in tension between the point of attachment of wheels 150 and fasteners 132, 134. As can be seen from FIG. 2, both links 128 and 130 are placed in bending moment by the load 234.

In another example, it may be assumed that the plate 54 contacts a high load item, for example a bottle, midway between the parallel planes defined by the respective edges of scissors links 128 and 130. Such a high load item is represented by the arrow 236 in FIG. 2. This tends to pivot the pressure plate 54 and reaction structure 138 in a clockwise direction about a horizontal axis extending through the bearing element 66. The web or track 208 tends to move toward wheels 180 to place the link 130 in compression between a point of attachment to wheels 180 and fasteners 132, 134. Meanwhile, the wheels 178 move into bearing engagement with web 220 to place that portion of link 130 in tension between its point of attachment to wheels 178 and fasteners 132, 134. correspondingly, wheels 150 bear against the web 224 of the reaction structure 140 and place link 128 in compression between its point of attachment to wheels 150 and fasteners 132, 134 while,

at the same time, flange 204 moves toward wheels 152 to place link 128 in tension between its point of attachment to wheels 152 and fasteners 132, 134. Thus, again, both links 128 and are exposed to a bending moment.

It will be noted that any tilting of the plate 54 from the horizontal is a function of the spacing of the wheels 152, between the flanges 204 and the web 208 and the spacing of the wheels 150, 178 between the flanges 220 and the web 224. It will also be noted that the minor degree of tilting, if any, of the pressure plate 54 does not bind the screw 64 since the lower end thereof is joumalled by the bearing element 66 nor is the threaded connection between the sleeve 76 and the screw 64 in a bind since the sleeve 76 is joumalled by the bearing element 78. Accordingly, the force output of the screw 64 is not substantially diminished when an eccentric load is contacted.

In another example, it may be assumed that the pressure plate 54 contacts a high load item represented by the arrow 238 in FIG. 3. This tends to pivot the pressure plate 54 and reaction structure 138 in a counterclockwise direction as seen in FIG. 3 about a horizontal axis extending through the bearing element 66. Eccentric loads of this type create bending moments in the links 128, 130 since the right hand portion thereof in FIG. 3 is in compression while the left portion thereof is in tension. Because of eccentric loading of this type, it has been found desirable to provide the link 130 with sections that are box-shaped in cross section to better withstand the bending loads.

It will accordingly be apparent that the compacting means 28 of this invention delivers a constant compacting force through the screw 64 while the maintaining means 58 acts to maintain the pressure plate 54 generally horizontal during compacting and does not bind the screw 64 nor otherwise diminish the output thereof regardless of the eccentricity of the load.

We claim:

1. A compactor comprising a frame providing a compacting chamber having an access opening thereinto;

a door mounted for movement between positions opening and closing the access opening;

means for holding an open top container within the chamber;

a pressure plate for movement into and out of the container for compressing refuse therein;

means for vertically reciprocating the plate including a generally vertical screw and means mounting the plate on the screw; and

means for driving the screw; and

means bearing between the plate and the frame independently of the screw for maintaining the plate generally horizontal during downward movement into the container, said plate maintaining means comprising a first reaction structure rigid with the pressure plate providing a first generally horizontal trackway therealong;

a second reaction structure rigid with the frame providing a second trackway therealong parallel to the first trackway;

a scissors linkage comprising first and second links pivoted together intermediate the ends thereof;

means mounting the upper ends of the links in the second trackway; and

5. The compactor of claim 1 wherein the first and second links are pivoted together about an axis intersecting the screw.

6. The compactor of claim 1 wherein the first link comprises first and second plates on opposite sides of the screw and upper and lower cross members connecting the plates together adjacent the upper and lower ends thereof.

7. The compactor of claim 1 wherein the second link comprises a pair of members, box-shaped in cross-section, on opposite sides of the screw and means connecting the box-shaped members together. 

1. A compactor comprising a frame providing a compacting chamber having an access opening thereinto; a door mounted for movement between positions opening and closing the access opening; means for holding an open top container within the chamber; a pressure plate for movement into and out of the container for compressing refuse therein; means for vertically reciprocAting the plate including a generally vertical screw and means mounting the plate on the screw; and means for driving the screw; and means bearing between the plate and the frame independently of the screw for maintaining the plate generally horizontal during downward movement into the container, said plate maintaining means comprising a first reaction structure rigid with the pressure plate providing a first generally horizontal trackway therealong; a second reaction structure rigid with the frame providing a second trackway therealong parallel to the first trackway; a scissors linkage comprising first and second links pivoted together intermediate the ends thereof; means mounting the upper ends of the links in the second trackway; and means mounting the lower ends of the links in the first trackway.
 2. The compactor of claim 1 wherein the mounting means comprise wheels.
 3. The compactor of claim 1 wherein the maintaining means further comprises a third link pivotally connected at one end thereof to the first reaction structure at a location coplanar with the first trackway and at the other end thereof to the first link, the second and third links being parallel.
 4. The compactor of claim 3 wherein the pivot axis of the third link at the one end thereof intersects the screw.
 5. The compactor of claim 1 wherein the first and second links are pivoted together about an axis intersecting the screw.
 6. The compactor of claim 1 wherein the first link comprises first and second plates on opposite sides of the screw and upper and lower cross members connecting the plates together adjacent the upper and lower ends thereof.
 7. The compactor of claim 1 wherein the second link comprises a pair of members, box-shaped in cross-section, on opposite sides of the screw and means connecting the box-shaped members together. 